Overload clutch



NOV 1, 1966 L.. H. BEcKr-:R'ETAL 3,282,387

OVERLOAD CLUTCH Filed oct. so, 1964 by a spring or the ilike.

United States Patent() 3,282,387 OVERLOAD CLUTCH n Leonard H. Becker, Country'Club Hills, and`Ronald H. Kenny, Addison, Ill., assignors to` Commercial Cam & Machine Co., Chicago, Ill., acorporation'of Illinois'` Filed Oct. 30, 1964, Ser..No.407,675 7 Claims. (Cl.I192-150) This invention relates to an overload clutch of the. det-ent type and the following disclosure thereof lis of fered for pub-lic .dissemination upon the Igrant of apatent therefor.

Ball types of detents -a-re commonly used in clutches but require a greater movement to 4-release than does a tapered button end type of detent las employed in ,the present invention. Thus, embodiments fof the present 'invention can be made substantially more compact for` the same load rating than isposs'ible with` prior art clutches. A correlate is that within the same space limitations,A greater spring preloads may be employed with embodiments of the present invention than can be achieved with a ball type detent. This results in a higher :torque rating for the clutch.

Another important advantage achieved by embodiments of the present'inventiou is decreased wear when contact between the two is. a point contact. All of the:

force provided by the compressed release spring `is carried by this point contact. Even under ideal conditions this can result in considerable wear. In the ypresent invention` the contact. is a substantial area, so that the .pressureper unit of contact area is greatly diminished. This decreases clutch wearyand increases clutch life.

In embodiments of the present invention the parts, 'and particularly the contact 'surfaces of the detent `and its seat, need not be formed -with that degree of accuracy required of a ball detent type clutch. With a ball, the angleyof contact betweenthe ball and its seat chan-gesV very rapidly with a change in the depth t-o which-the ball is received 4in i-tsseat. .A seat/contact angle correct for one depth of seating of a ballvis entirely wrong foranother depth of, seating of the ball. i

- The detentsl of the present invention are directlyl loaded.

are indirectly loaded by a spring, eg. lheld* in place byv another detent which in turn is spring loaded,-they are more readily Icalibrated in. terms of torquerequired to produce clutch release. Whenzoalibrated, they are moreaccurate as to the torque required 4to cause clutch release, timeafter time.

"It has been found that the seating .angle of the detent i-simportant in obtaining smo-oth clutchrelease,and little clutch parts. The `smooth clutch release .action "is one of the significant fact-ors in producing embodiments wherein' the clutch will release rat a predetermined torque. l'Binding and frictional changes kcan affect Ithe amount of torque required to cause clutch release withfdetent type clutches.

Further objectsI and advantages will -be apparent from As comparedt-o detents that.

ice

thefollowing'description taken in conjunction with the drawings, inwhich:

FIGURE 1 is anelevational view, partly in section, of an loverload olutch'rnechanism, in accordance with this invention, inl driving relation;

FIGURE 2 is 'a fragmentary view of thepart-s shown in FIGUREul, in overload position; .and

FIGURE 3 is a perspective view of a plunger, as shown in the other figures with a'flat and chamfered endv but-ton.

Although the following disclosure offered for public dissemination isdetailed to ensure adequacyy rand aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how'others may later disguise itby rva-r-iationszin form or additionsor further improvements. Theclaims at the end hereof a-re intende-d asthe chief aidtoward this purpose; as itis these that. meet the requirement of pointing out the parts, improvements, or combinations in which the inventive concept are found.

Referring now more particularly to the drawings, la driver 10, which m-ay be .an electric motor, has a driving plate 12 secured to its output shaft 11. A plunger or detent carrying plate 14 is attached t-o driving plate |12 by a,4 number ofbolts 16. A driving cap 18 is 'also secured against the outside of the carrying plate 14 by the same bolts 16 extending through the cap 18l and plate .14. Bolts 16` have .threads engaging in the plate l12., and heads 20 engaging th-e -outside of the .cap 18.

lthe plunger'plate -14. The inner end of cap 18 for-ms a Vbattering as the detents reseat upon eachfrevolution ofthe sh0ulder22-of reduced diameter. Inthe space between the plate 14 .and the cap 1-8 and upon the shoulder 22 of the cap .are mounted adriven `rnember'24 and a Wear plate 26. The driven member may bea gear, dia-l'plate, sprocket or the like. The wear plate .26 and driven member 24 are secured together `for joint .operation by registering=dowel openings 28 and'30 and dowel pins 32. Wear plate 26 has an inner diameter to fit on'the reduced shoulderfZZ ofthe capancl Ian outer diameter to t-he same asthatof the plunger-.plate 14. The openings 30 of the wearplate are covered. by the outer side-of plunger plate 14.,

In the corresponding outer portion of the plunger plate 14vare1plunger-ordetent receiving openings 34 extending therethrough lat right angles. These openings are open for-the. full size at the outer or wearplate side, but having a reduced opening 36 at -t-he inner side. In the correspending ROI-tins of the Wear plate 26,. and spaced-'from the dowel openings 30, are recesses to receive the detent or plunger heads 46. Eachrecess has a reduced .portion 38 smaller in diameter than the adjacent plunger opening 344 and a chamfered connecting opening 40 increasing to the full size of plunger opening 34 at the inner side of the wear plate 26.

With this const-ructionaplunger or 'detent 42 may be having one end bearing against the abutment about the reduced opening 36. The other end of the spring bears against head 46 `thereby tending to press the button head toward the wear plate 26.

Button 'head 46 has a-n outer charnfered surface 50 being tlhe frustum of `a cone. The angle of charnfer corresponds to the surface about opening 40 in the Wear plate 2'6. The diameter of the outer surface 51 of the heard `46 determines the-contact area between the detent and the wear plate 26 :when the clutch is disengaged. The amount of wear by this contact will be a :function of the spring pressure |and this contact 'area (other conditions being equal). The spring pressure will be determined by the maximum torque which the clutch is to transmit Vbefore 'disengagement takes place. To produce a clutch with la satisfactory operating life the diameter of surface 5.1 should have |at least a diameter as large as that determined by the following formula:

l P D Z 500W D=The minimum diameter of the surface 51, and P=the maximum spring force durin-g an overload, in

pounds. The angle of charnfer of the detents is important to obtain a smooth operating clutch that will maintain en- Wherein:

gagernent until the overload torque is reached Iand then the detents thereof will promptly and easily unseat. The chamfer forms the frustum of a cone. This cone should have an apex angle of :between 70 and 100 to achieve thefrequired smooth operation. In the illustrated e-mbodiment the cone, of which the chamfered portion 50 is a part, has an apex angle of 90.

The plungers 42 are `connected-by fastening screws 54 to a detector plate 52 positioned in the space surrounding the driving plate i12, between the motor or driver 10 Aand the plunger carrying plate 14. A snap action switch 58, e.g. a microswitch, is mounted so that its actuating plunger 56 will be operatively acted upon by detector plate 52 when the detents are unseaterd. This is illustrated in FIGURE 2. Under normal conditions, as shown in FIGURE 1, there is no contact between plate 52 and plunger 56. Switch,58 is employed to signal the existence of the overload causing clutch disengagernent, such signal usually 'being in the lform of deenergizing the ydrive Imotor.

The space between plate 52 and plunger 56 can be very small, much smaller than the lineal movement of the detent-s upon clutch disengagement. Thus a signal is quickly given, even before the clutch has ttiully disengaged. In -a typical embodiment the detector plate rises 0.093 inch Ito completely disengage the clutc'h, but the limit switch signals or effects a power shut-off upon a movement of only .005 inch, i.e. substantially before the clutch is completely disengaged. When the overload condition is corrected Iand the detents are realigned with their seats, the springs 48 automatically return the plungers 42 to full engagement ready for normal operation. l

It is significant that these features can be incorporated into an overload clutch which permits a parallel misalignment up to %4 of an inch and an angular misalirgnment up to 1/2 degree with zero backlas The plun'gers 42 tare each Iguided at one end by stern 36 and 'at the other by hea-d 46. `This guidance at both ends :gives la smooth action and eliminates binding. It also provides a central area for locating the spring in a mannerthat assures a minimum overall length and-,contributes to the comp-actness Aof vthe clutch.

We claim: i' i v 1. In an overload clutch, comprising a driver member, a driven member rotatable with respect thereto and a releasable connection between the members, the improvement comprising a plunger plate movable with the driver member and having transverse openings near the outer edge, said openings each having a first portion which is cylindrical through most of the plate and a second portion which is reduced in size at one side, plungers movable end wise in the transverse openings,` each plunger having a button head at one end to slide in said first portion of said opening and a reduced stem in said second portion of said opening, thereby guiding the plunger at both ends, a wear plate secured to the driven member in juxtaposition to the other. side of the plunger plate and having chamfered openings registering with the plunger openings, each plunger having a flat end at the outside of the button head with chamfered edges to register with one of said Wear plate chamfered openings, and a coil spring surrounding the stemof each plunger in the first portion of the plunger opening and engaging the under side of the button head at one end and the wall of the plunger plate surrounding said second portion of the plunger opening at the other end.

. 2. In an overload clutch as set forth in claim 1, a cap having an outer ange of the same general external configuration as the outside of the plunger plate and with a reduced shoulder on the inner side of the cap forming a space with said first portion of the plunger opening of the `plunger plate at one side, the driven member and the wear plate Ibeing mounted on saidreduced shoulder and confined in'between the cap flange and the plunger plate so the chamfered openings of the wear plate will engage the chamfered end of the corresponding plunger, and means engaging the driven member and the wear plate for holding them together in driving relation.,

3. In an overload. clutch as set forth in Iclaim 1, wherein the at end of the button head is circular and has a minimum diameter determined by the formula: the mnimum diameter in inches equals two multiplied by the square root of the spring pressure in pounds divided by five hundred pi.

4. In an overload clutch as set forth in claim 1, wherein said button head is cylindrical and the chamfered edges thereof form a frustum of a cone having an apex angle of between 70 and 100.

5. An overload clutch as set forth in claim 1 in which each plunger is longer than the thickness of the plunger plate to engage the wear plate at the head end and the stem projecting from the plate at its opposite side, a detector plate at said one side of the plunger plate, mounting means connecting the detector plate to the clutch in a positionfto contact the stem end of a plunger, the detector plate being axially movable with said plunger, and an electrical limit switch having an actuating means engaged 'by the detector' plate in its longitudinal movement to actuate said switch to initiate a signal for indicating the overload.

6. vIn an overload clutch of the detent type wherein a plurality of detents carried by one member normally seat in recesses in another member and are unseated by an overload to-permit the other member to rotate with respect to said one member, the improvement comprising: said one member having a detent receiving opening for each detent, each opening being a large cylinder at the side of the one member adjacent the other member, said one member having a wall at the other side thereof with a'small opening therethrough, said small opening being coaxial with the large opening, each detent having a 'button head slideably received in the large opening and a stem slideably received in the small opening, said button head having a flat, circular, end opposite said stem and chamfered edges about said end, said recess having vchamfered sides, said chamfered edges and sides being a frustum of a cone having an apex angle of between 70 and a coil spring in said large opening and about said stem with one end thereof abutting said wall and the other end thereof abutting said head, said spring urgby the square root of the spring force in pounds divided by ve hundred pi.V

7. In a clutch as set forth in claim 6', including a detector plate positioned at said other side of the one member, secured to the stems of the detents and moveable therewith, stationary iswitch means, and actuating means operatively interconnecting said switch means and said plate to actuate said switch means by movement of the plate resulting from the detents 'becoming at least partially unseated from said recesses.

2,148,481 2,167,749 2,209, ISS 2,232,545 2,856,046

References Cited by the Examiner UNITED STATES PATENTS DAVID J. WILLIAMOWSKXQPrimary Examiner.

A. T. MCKEON, Assistant Examiner. 

1. IN AN OVERLOAD CLUTCH, COMPRISING A DRIVER MEMBER, A DIRVEN MEMBER ROTATABLE WITH RESPECT THERETO AND A RELEASABLE CONNECTION BETWEEN THE MEMBERS, THE IMPROVEMENT COMPRISING A PLUNGER PLATE MOVABLE WITH THE DRIVER MEMBER AND HAVING TRANSVERSE OPENINGS NEAR THE OUTER EDGE, SAID OPENINGS EACH HAVING A FIRST PORTION WHICH IS CYLINDRICAL THROUGH MOST OF THE PLATE AND A SECOND PORTION WHICH IS REDUCED IN SIZE AT ONE SIDE, PLUNGERS MOVABLE END WISE IN THE TRANSVERSE OPENINGS, EACH PLUNGER HAVING A BUTTON HEAD AT ONE END TO SLIDE IN SAID FIRST PORTION OF SAID OPENING AND A REDUCED STEM IN SAID SECOND PORTION OF SAID OPENING, THEREBY GUIDING THE PLUNGER AT BOTH ENDS, A WEAR PLATE SECURED TO THE DRIVEN MEMBER IN JUXTAPOSITION TO THE OTHER SIDE OF THE PLUNGER PLATE AND HAVING CHAMFERED OPENINGS REGISTERING WITH THE PLUNGER OPENINGS, EACH PLUNGER HAVING A FLAT END AT THE OUTSIDE OF THE BUTTON HEAD WITH CHAMFERED EDGES TO REGISTER WITH ONE OF SAID WEAR PLATE CHAMFERED OPENINGS, AND A COIL SPRING SURROUNDING THE STEM OF EACH ENGAGING THE UNDER PORTION OF THE PLUNGER OPENING AND PLUNGER IN THE FIRST SIDE OF THE BUTTON HEAD AT ONE END AND THE WALL OF THE PLUNGER PLATE SURROUNDING SAID SECOND PORTION OF THE PLUNGER OPENING AT THE OTHER END. 